I would also add that, at the end of the day, our underlying data model only supports straight line segments so any tools in editors which support easy creation of more complex shapes have to approximate them via straight lines.

I think about JOSM and Potlatch. Of course, the mathematic model (clothoid) should be only use to optimize the geometry (like in Potlatch2 the option "make circular". This is the same idea behind.. Do You speak German?